Veterinary clinics and animal shelters across the country could soon be streamlining their canine castration protocols, thanks to a product that's gaining popularity in the veterinary community. A nonsurgical, injectable sterilant for male dogs is scheduled for release in the United States this year and could prove to be stiff competition for the traditional surgical method of castration.

Zeuterin, a chemical compound of zinc gluconate neutralized with arginine, has been in use in Mexico, Colombia, Bolivia and Panama for a few years under the name Esterilsol and has proven to be a successful method of sterilization in male dogs at least three months of age, according to Ark Sciences, the company that developed the product. Now scheduled for release in the U.S., the injectable formulation is being marketed to induce permanent sterility without the need for general anesthesia or a surgical incision. It is currently FDA-approved for use in dogs three to ten months of age and is available only to licensed veterinarians who are trained by Ark Sciences in the injection technique. Sandeep Manchanda, a member of Ark Science's executive team, says the company is focusing heavily on educating and training veterinarians about the product and the administration technique.

According to Ark Sciences, the product acts as a spermicide and results in permanent and irreversible fibrosis of the testicles. The testicles eventually atrophy and diminish in size, although they will still be visible. As such, animals that are sterilized with this technique are tattooed in the groin area to indicate that they've had the procedure performed. Although infrequent, clinical side effects have been reported to be associated with the product and include testicular swelling and pain, vomiting and injection site reactions. However, the company asserts that proper technique and light sedation for the animal can decrease the occurrence of some of these adverse effects.

Ark Sciences is focusing its initial launch efforts on the nonprofit sector and already has product training in place for a number of shelters and spay-neuter clinics across the country. Additionally, Zeuterin has generated interest from many animal welfare groups and organizations such as the Alliance for Contraception in Cats and Dogs (ACC&D), a group whose core mission is to advance development of nonsurgical sterilization in cats and dogs.

Karen Green, senior director of ACC&D, has been following the development and use of the product internationally for years and is looking forward to its pending release in the United States. "In the U.S., the greatest potential is that it can save many organizations a lot of time, money and space. One of the limitations for some spay-neuter programs is recovery space for animals after surgery. With Zeuterin, the animals don't have to undergo anesthesia and they can be up and ready to leave pretty quickly, since it's an outpatient procedure. That can make it possible for organizations to use fewer resources to sterilize male dogs, leaving them with more resources for spaying females or for their other programs, such as adoption or education."

But even the strongest proponents of the product realize that it may take time for the veterinary industry—private practitioners in particular—to embrace this form of sterilization. "It's a bit of a paradigm shift," says Byron Maas, DVM, a master trainer for the product. "Veterinarians already have the tools to do surgical spays and neuters, so why change? The fact is, some clients may be worried about anesthesia or the invasiveness of surgery. There is a market for this type of neutering in the veterinary community and we, as veterinarians, can offer it to clients as an alternative to traditional castration." Maas, who is also a private practitioner in Bend, Ore., and a longtime advocate for population control in companion animals, stresses that this product is different because it's being made available only to trained veterinarians. "The focus is on the veterinarian understanding the product and using it correctly," he says.

Ultimately, Ark Sciences hopes that Zeuterin will overcome the barriers known to prohibit reduction in the intact dog population, such as time, money and available resources. "We may be able to get to a larger population of male dogs that surgery alone hasn't been able to," Manchanda says. "Our vision and goal is full adoption of any dog that is considered adoptable in this country."

Ark Sciences expects to launch Zeuterin by the end of 2012. More information on the product can be found at www.arksciences.com.